Ch 4: Host Pathogen Relationships Flashcards
Pathology is the study of ____
Disease
Etiology is the study of _____
Cause of disease
What is Pathogenesis?
Disease process
What is infection?
Colonization by microbe
______ is the degree of pathogenicity
Virulence
What is bacteremia?
Presence of bacteria in the blood
______ is generalized inflammatory response to an infection
Sepsis
Difference between infection vs disease?
Infection is invasion by parasitic microbes (can occur without causing disease)
Disease is changes in health, damage to host.
Name the phases of disease
Incubation: time between introduction of organism to onset of symptoms
Illness: individual experiences signs and symptoms of disease
Convalescence: period of recuperation and recovery, infections diseases may still spread
Who provided the first scientific definition of sepsis: “sepsis is a state caused by microbial invasion from a local infectious source into the bloodstream which leads to signs of systemic illness in remote organs”
Hugo Schottmuller
ToF: Commensalism is when one benefits and the other neither benefits or is harmed
T
ToF: Mutualism is when both organisms benefit
T
What type of host pathogen relationship is when one organism benefits and the other is harmed?
Parasitism
ToF: Opportunistic pathogens normally cause disease
F: Do not normally cause disease, but may under some circumstances (Normal flora in wrong environment, compromised immune system, disruption of homeostasis)
Name four portals of entry of pathogenic microorganisms
Mucous membranes, skin, parenteral, placenta
ToF: Mucous membranes of the respiratory tract are the easiest and most frequent portal of entry
T
How is the mucous membranes of the respiratory tract a portal of entry for pathogens?
Microbes are inhaled into mouth or nose in droplets of moisture or dust particles
How is mucous membranes of the GIT a portal of entry?
Microbes gain entrance through contaminated food and water or fingers and hands
Most microbes that enter the GIT are destroyed by ____ and ______
Hydrochloric acid and enzymes of the stomach and small intestine
Which diseases commonly enter through mucous membranes of the genitourinary tract?
Sexually transmitted diseases
Ex. Gonorreah, Syphilis, Chlamydiasis, HIV
How do microbes enter through mucous membranes of the conjunctiva?
Mucous membranes that cover the eyeball and lines the eyelid
ToF: Herpes ocularis commonly enters the body through mucous membranes of the conjunctiva
T
Name two common diseases contracted via the skin?
Staphylococcus infections and Mycosis
ToF: The skin is not an effective barrier for microorganisms to enter
F: When unbroken it is an effective barrier
Some microbes can gain entrance through openings in the skin (hair follicles and sweat glands)
What is the parenteral portal of entry?
Microorganisms deposited into the tissues below the skin or mucous membranes through: punctures, injections, bites, scratches, surgery, etc.
Name three common diseases contracted vis parenteral
Cytomegalovirus, Hepatitis, HIV
What does LD50 mean?
Number of microbes in a dose that kills 50% of the organisms infected in a sample
ToF: ID50 is the number of microbes in a dose that kill 50% of the organisms infected in a sample
F: ID50 is the number of microbes in a dose that causes disease in 50% of the organisms infected
Name and describe the three steps of pathogens invading an organism
- Adherence: pathogens have attachment structures (ex. Pili)
- Invasion/Colonization: multiply (need food, water, space) and protect from host defenses (must compete with normal flora, immunity, etc.)
- Cause damage: tissue destruction (ex. Toxic byproducts and degradation enzymes), production of toxins, escape of host defenses
What is immunopathogenesis?
Excessive innate, immune and inflammatory responses triggered by the infection (superantigens; immune complexes precipitation)
What is a virulence factor?
A pathogen-produced substance that promotes the establishment and maintenance of disease
What are the types of virulence factors?
Adhesion factors, evading immune response, degradative enzymes, and toxins
What are some adhesion factors?
Pili: short, rigid and numerous
Adhesions: molecules that bind to specific receptors on tissues
A _______ prevents phagocytosis by macrophages or neutrophils by not being ‘seen’ by these cells
Capsule
__________is when antigenic similarity occurs between molecules found on some disease-causing microorganisms and specific previously healthy body cells/tissues
Antigenic mimicry
What is antigenic shift?
Genetic alteration occurring in an infectious agent that causes change in antigen protein.
This stimulates the production of antibodies by the host immune systems
ToF: Antigenic shift had been studied in influenza type A viruses
T: they experience this change once every 10 years
Describe how the inhibition of phagolysosome fusion that allows pathogens to avoid immune response
Bacteria is enclosed in phagosome and lysosome needs to fuse to destroy it. They stop this fusion and bacteria stays alive in the phagosome
______ attack certain types of white blood cells, preventing phagocytosis. They release and rupture lysosomes
Leukocidins
What do hemolysins do?
Cause the lysis of red blood cells.
Ex. Streptococci
What do coagulase do?
cause blood to coagulate, blood clots protect bacteria from phagocytosis from white blood cells
Ex. Staphylococci (causes boils and abscesses)
ToF: Kinases dissolve blood clots
T
ToF: Kinases do not help the spread of bacteria (bacteremia)
F
What is the mechanism of Hyaluronidase?
Breaks down hyaluronic acid (found in connective tissues) and is a spreading factor.
It also allows bacteria to use hyaluronan as a carbon source
Which of the following is produced by Streptococci, Staphylococci and Clostridium?
A) Kinases
B) Collagenase
C) Hemolysis
D) Hyaluronidase
D) Hyaluronidase
ToF: Collagenase breaks down collagen
T
ToF: Colstridium perfringens uses kinases to spread through muscle tissue
F: uses collagenase to spread through muscle tissue
What is a necrotizing factor?
Causes death (necrosis) to tissue cells
Caused by Streptococcus class A (flesh eating bacteria)
What are toxins?
Poisonous substances produces by microorganisms (can be exotoxins or endotoxins)
What is it called when toxins are in the bloodstream?
Toxemia
ToF: Exotoxins are released intracellular
F: released extracellularly
How do Leukotoxins function?
Invoke a very strong immune response, affect T cells which release a lot of cytokines that cause severe symptoms
How do cytotoxins damage tissues?
Disrupt host plasma membrane by targeting protein channels and phospholipid disruption
What pathogen is responsible for causing symptoms of botulism, prevention transmission of signal from nerve cell to muscle cell?
Clostridium botulinum
What pathogen is responsible for the symptoms of tetanus?
Clostridium tetani
ToF: Clostridium botulinum and Clostridium tetani are examples of neurotoxins
T
ToF: Endotoxins are present in Gram positive bacteria
F: Gram negative bacteria
ToF: Endotoxins are part of the outer portion of the cell wall
T: the lipid A portion of
ToF: Endotoxins are not very stable and can be destroyed easily
F: they are very stable and cannot be destroyed easily
Macrophages release _____ when they attack some gram negative cells. This binds to many tissues of host and may cause to blood capillaries and the blood brain barrier.
Tumor necrosis factor (TNF)
What is the main symptom of endotoxins?
Pyrogenic response:
Macrophages ingests gram negative bacteria
Release interleukin-1 in bloodstream
IL-1 travels to hypothalamus and produces prostaglandins and it reset the body’s thermostat
Name factors effecting susceptibility to resistance of host
Age, stress, diet, pre-existing disease, gender, behaviour, weather and the first line of defense
What type of toxin causes leukopenia followed by leukocytosis, activation of complement, thrombocytopenia, disseminated intravascular clotting, loss of eater and decrease in blood pressure, and eventually death?
Endotoxin
